1. Field of the Invention
The present invention generally relates to magnetic disk drives and flexible printed boards used in the same, and particularly relates to a magnetic disk drive having a servo head and read/write heads (magnetic heads for recording and reproducing information), and to a flexible printed board connected to the read/write heads and the servo head.
The read/write heads are used for recording and reproducing data for magnetic disks, and the servo head is used for reading from a magnetic disk servo signals which control the positions of the read/write heads.
Keeping pace with a trend of down-sizing and the development of computer systems having a higher processing speed and a larger information storage capacity, magnetic disk drives used as an external storage device are subject to a demand for miniaturization. Also, each component in the magnetic disk drives is required to be implemented with a higher density.
2. Description of the Prior Art
In the magnetic disk drives of the prior art, servo information is read out from a servo surface of a magnetic disk, and the magnetic heads (read/write heads) for recording and reproducing information are positioned on a desired track based on the servo information. Such magnetic disk drives have the read/write heads as well as the servo head on arms thereof. Also, on the actuator thereof are mounted a servo semiconductor devices (servo IC) which are connected with the servo head, and recording and reproducing semiconductor devices (read/write head IC) which are connected with the read/write heads.
When data is read or written, a large amount of electric current tends to flow in the read/write head ICs. This is so, especially when data is written. Thus, if a read/write head IC is provided near a servo IC, an electric current in the read/write head IC can bring about noise in the servo IC, especially when data is written.
The same can be observed if signal lines connecting between a read/write head and a read/write IC for recording and reproducing information is placed in a proximity of servo signal lines connecting a servo IC with a servo head. Namely, an induction noise is generated from the read/write-head signal lines by electromagnetic induction. This induction noise affects the servo signal lines to cause servo noise within servo signals.
If the read/write head IC or the read/write head-signal lines have a harmful effect on the servo heads or the servo signal lines, the positioning of the actuator deteriorates because of disturbance on servo signals.
In the prior art, magnetic disk drives such as the following have been proposed to address the problems as described above.
A first type of such a magnetic disk drive is characterized in that read/write-head signal lines are placed as far as possible from the servo signal lines and also not in parallel to the servo signal lines.
A second type of such a magnetic disk drive is characterized in that a read/write-head and a servo head opposing each other are provided on an actuator at staggered positions, whose displacement is in a direction of the circumference of a magnetic disk or a direction of the revolving movement of the arm.
A third type of such a magnetic disk drive is characterized in that a servo head and a read/write head are not mounted on the same arm.
In the magnetic disk drives of the first and the second types, an arm on which a read/write head and a servo head are mounted inevitably become large. This leads to an enlargement of an actuator.
In the magnetic disk drive of the third embodiment, different arms are provided for the servo head and the read/write head, which leads to an increase in the arm weight. Thus, a larger electric power is required for a voice coil motor driving the actuator. Also, preparing separate arms for servo heads results in an enlargement of the actuator size.
Accordingly, there is a need in the field of magnetic disk drives for a magnetic disk drive which can be miniaturized and in which noise from wirings of read/write heads and read/write-head ICs does not have a harmful effect on wirings of a servo head and servo ICs, and for a flexible printed board used in such a drive.